This information offers an "early glimpse" version of data from the current month, and should not be used for analyses that require completeness or accuracy. The information is based on whatever data is available from as many of the station networks and data sources possible, and changes as new data becomes available or as data quality is improved. The datasets are modeled using climatologically-aided interpolation (CAI), which uses the long-term average pattern (i.e., the 30-year normals) as first-guess of the spatial pattern of climatic conditions for a given month or day. CAI is robust to wide variations in station data density, which is necessary when modeling long time series. See PRISM datasets for more information; data available from this page is type "AN81d." Individual grids may contain non-climatic variations due to station equipment and location changes and to station openings/closings. For information on when the grids were most recently updated, see calendar of PRISM data updates.

These datasets should be considered "early" (certain to change as new reporting stations are added and quality control measures are applied).